[sdiy] [OT] LM13700 spotted in commercial product of big Manufacturer

[Brian Willoughby]

On May 16, 2022, at 09:47, Benjamin Tremblay via Synth-diy <synth-diy at synth-diy.org> wrote:
> My problem is, until I see the round-trip process firsthand I just don’t know what to do.
> If I had someone else’s design and I could just send it off and then look at the assembled results, then tweak it a little and do another build, maybe then I would learn.

I'm not sure what your goal is, but if you just want to take advantage of assembly houses then the process is simple.

CAD software like EAGLE will export Gerber files and a CAD file, although the latter usually requires a second step (and a special EAGLE script). Some assembly houses will use the top silk screen layer as a guide for placing parts, others will use the CAD file, and at least one assembly house had different employees who used different files depending upon chance (as I found out when I re-ordered the same boards and got different results!).

The learning process is somewhat challenging because PCB fab houses and assembly houses don't seem to want to answer "how to" questions. Every time I called and asked, the answer always seemed to be, "We can work with whatever files you provide." They never mentioned that there are usually multiple ways to accomplish the same results, but it costs more to do things the hard way, and thus I was disappointed that they wouldn't give me any hints about how to design in a way that saved money. I was also disappointed that quotes weren't broken down in a way where you could see if some aspect of the design was costing way too much (like 4 mil trace width or something unnecessary like that).

Over the years - working with several fab houses in King County, WA - I've learned how to do this affordably within the US. A bonus is that you can create DRC (Design Rule Check) files that are specific to each fab. Then you can copy a PCB design, change the associated DRC, and the next Gerbers you create will be altered to match the available services. Smart shops like OSHPark will provide the EAGLE DRC file for you, and you can use that to check your PCB designs for compatibility with their services, as well as use it to create the Gerbers specifically for OSHPark.

I'm assuming that you're already designing PCB for yourself that are thru-hole, such that you stuff them yourself. If you're doing that, then changing to SMD and hiring assembly is almost no extra learning. But I realize that building ready-made PCBs is a HUGE part of the DIY market, and it's a big leap from there to DIY PCB design.

Brian Willoughby

p.s. I've not used any mail-order assembly (just mail-order PCB fab). My experience is all with a local assembly house where I could meet with the owners and discuss my lack of industry knowledge. But at this point I feel convinced that I could send the same files to China and get the same results for even less money (but longer delays, and potential TSA hold-ups).